Device for producing tubular bodies of semiconductor material, preferably silicon or germanium

ABSTRACT

A device for producing tubular bodies of semiconductor material, preferably of silicon or germanium. To this end, a rod or tube shaped carrier is heated in a reaction gas for precipitating the respective semiconductor, as a result of which the jacket area of the carrier is coated with a layer of the semiconductor. Following the removal of the carrier, this semiconductor layer defines the desired tube. At least two vertical carriers of carbon material, e.g. graphite, are each held at their lower ends by an electrode, and are connected at their upper ends by a conductive bridge, preferably of carbon.

[ July 17, 1973 United States Patent Dietze et al.

m m "t "e "n m V. m r d n 8 BS DEVICE FOR PRODUCING TUBULAR 3,058,812 Chu et al. BODIES or SEMICONDUCTOR MATERIAL, 2 v 5/ Henker e1 PREFERABLY SILICON 0R GERMANIUM $1966 [75] Inventors: Wolfgang Dietze, Munich; Konrad Reuschel; Herbert Sandmann, both of Vaterstetten, all of Germany Primary Kaplan Siemens Aktiengesellschaft, Munich, Germany Feb. 8, 1971 Appl. No.: 113,286

Att0rney-Curt M. Avery, Arthur E. Wilfond, Herbert L. Lerner and Daniel J. Tick [73] Assignee:

[22] Filed:

ABSTRACT A device for producing tubular bodies of semiconductor material, preferably of silicon or germanium. To

[30] Foreign Application Priority Data OCI. l2, l970 Germany P 20 50 076.9 this end a rod or tube shaped carrier is heated in a re.

M m 1 w m 4Mc2 2 .9; 2 3 @Mow4 /507 82 16 v c u M BW 6 52 2 n 4 m m h c n r u a u e U m l C 5 mfw .U [P 1 ll 2 8 5 55 l .ll

lI8/4849.5; 117/106 R, 106 A, 106 C D, 107.2, 228; 249/134, 82; 425/470, 438, 447

carbon material, e.g. graphite, are each held at their lower ends by an electrode, and are connected at their upper ends by a conductive bridge, preferably of carbon.

[56] References Cited UNITED STATES PATENTS 2,955,566 10/1960 Campbell et 118/49 X 10 Claims, 2 Drawing Figures Mm Hm I 3.746.496

Fig.2

m mama mum- DEVICE FOR PRODUCING TUBULAR BODIES OlF SEMICONDUCTOR MATERIAL, PREFERABLY SILICON GR GERMANIUM Our invention relates to a device for producing tubular bodies of semiconductor material, preferably of silicon or germanium, whereby a rod or tubular shaped carrier is heated in a reaction gas able to precipitate the respective semiconductor, so that the outer jacket area of the carrier becomes coated with a layer of semiconductor material and, after removal of the carrier, defines the desired tube.

The invention provides that at least two vertical carriers of carbon are each held at their lower end by an electrode and that their upper ends are interconnected via a conductive bridge, preferably of carbon.

This device shows similarities to a certain known device for producing semiconductor rods, particularly of highly pure silicon, wherein rod shaped original carriers of polycrystalline or monocrystalline silicon are arranged, similarly as the carriers in the method according to the invention, in a reaction vessel and are heated to the high temperatures necessary for precipitation by electric current, more particularly an alternating current, supplied via the electrodes. However, a successful production of tubes of semiconductor material, re

quires further features which permit a disturbance free removal of carriers from the semiconductor layer which defines the tube and is preferably polycrystalline. These features, however, are not customary during precipitation for the production of rod shaped semiconductor crystals.

Tubular carriers are, preferably, used in the method according to the invention, which are passed by a cooling gas, particularly argon or nitrogen or by a liquid coolant, while the precipitation of the respective semiconductor material takes place at their outside. This important feature specifically promotes the separation of the silicon and germanium layers from the carriers and the formed tubes can be removed from the carriers without difficulty so that they may be reuseable.

Accordingly, a preferred embodiment of the device, according to the invention, is so characterized that at least one carrier intended for precipitation is tubular in shape and designed as a flow channel for an electrically insulated, gaseous or liquid coolant.

In the Drawing:

FIG. 1 schematically illustrates the situation where a precipitation may take place at both carriers, or only at one carrier; and

FIG. 2 illustrates both carriers positioned concentrically, relative to each other.

In FIG. 2 the inner carrier serves as a connecting bridge, not simultaneously as a carrier for precipitation. The carrier insures, however, a uniform heating of the outer carrier by serving as a substrate for the semiconductor layer.

The device shown in FIG. 1 comprises a bottom plate 1 of quartz or a heat resistant inert metal, which is hermetically connected with a quartz bell 2. In the interior of this reaction chamber defined by parts 1 and 2, are situated two vertical, tubular carriers 3, one end of each being inserted with their ends into appropriate bores 4 of respective supporting electrodes 5. The electrodes are in conductive connection with the leads 11. The leads 11 are led through the bottom plate 1 of the reaction vessel, in mutual insulation.

The upper ends of the vertical tubular carriers 3 are interconnected with a conductive bridge 6, preferably of the same material as the carriers 3. The upper ends are inserted into bores 7 of the bridge 6. A correspond ing geometrical adjustment insures an impeccable, electrical contact. The bores 7 are tapered somewhat upwardly while bores 4 are somewhat tapered in a downward direction so that the tubular carriers 3 are seated in electrodes 5 and in the bridge 6 as closures. The interior of the tubes 3 is open toward the reaction chamber via bores 7 so that a gaseous coolant reaches the reaction chamber, flowing via a respective lead 8, led through the bottom 1 of the reaction vessel via the bores 4 in the electrodes 5 and flowing into the tubular carriers 3. In this instance, the coolant is either hydrogen, which as a reduction agent, is a direct participant in the reaction process or else it functions as an inert gas, for example, argon or nitrogen, which serves only as a diluent for the active components of the reaction These reaction gases constituting,for example in the case of silicon, a mixture of SiHCl or SiCl and hydrogen, if necessary, together with a gaseous dopant, are admitted into the reaction chamber, through an inlet 9 which is situated centrally in the bottom 1 of the reaction vessel. Positioned concentrically thereto, is the outlet tube for the consumed gas. The inlet 9 protrudes somewhat further into the interior of the reaction vessel than the outlet line 10, which surrounds the former in concentrical relation and is located exactly between the two tubular carriers 3. The fresh reaction gas must be admitted, in this device, with an appropriately high pressure so that a defined jet forms in the reaction chamber.

Precipitation is effected in the usual manner. Semiconductor layers 12, for example of silicon, germanium, SiC or A B compounds, then form at the outer jacket areas of the tubular carrier 3, which can be removed without effort from the tubular carriers 3 after the device has cooled down.

It is important, however, that the temperature at the outer side of the carriers 3 does not exceed, in the following cases, the following temperature below 1,250C, as the carbon carrier would otherwise react with the semiconductor and the tubes would no longer be easily peeled off from said carrier. These temperatures are:

1250C for silicon 900C for germanium 1l50C for GaAs 1300C for SiC 850C for lnSb The carriers 3, the bridge 6 as well as electrodes 5, preferably consist of the same graphite type, the ducts (entrances) 8, 9, R0 and ll through the bottom plate, preferably consist of a resistant metal. The current conducting parts must be in mutual electrical insulation, via a suitable insulating layer.

In the device illustrated in FIG. 2, a bottom plate I is also provided as well as a quartz bell 2 which is hermetically connected therewith and which together form the reaction chamber. At a central location, a system of electric leads 13 and 14 in mutual concentric position and in hermetic and mutual electrical insulation, are led through the bottom 1. The innermost electrode 13 is also tubularly shaped. Both electrodes are profiled at theirupper front faces, in the interior of the reaction vessel. With the aid of this profiling and of an appropriate profiling (opposite to the first) at the low front faces of both graphite carriers 15 and 16, the latter are seated upon carbon electrodes 13 and 14. The coolant not only flows in the space between the carriers 15 and 16 but also via openings 17 in the interior of the carrier 15. The inner tubular carrier 15 continues directly into the outlet for the coolant, defined by the interior of the tubular electrode 13. In the vicinity of its upper end, the wall of the interior carrier is provided with opening 17, which constitutes a continuous connection to the space between both carriers and 16. The inner space is provided with fresh coolant by two or more inlets 8, arranged in symmetry to the interior carrier 15. The coolant at inlet 8 enters the system of both carriers 15 and 16 and emerges therefrom at location 10. The reaction gases enter at 9 and the waste gases exit at 20.

The upper ends of both carriers 15 and 16 are fitted into appropriate recesses of the bridge 18 which connects them. This bridge 18 is disc-shaped and closes the interior of the inner carrier 15, as well as the intermediate space formed between both carriers 15 and 16 to the actual reaction chamber outside the carrier 16 and against the reaction gas, located therein.

When the cross section of the connecting bridge 18 between the carriers is so large that the heating of this bridge does not suffice'for precipitation, a bilaterally open tube 12 develops, as shown in FIG. 1, otherwise as shown in FIG. 2, a tubular cup 12 results.

It is recommended that not only the carriers 3 and 16 be coated, but also the connecting bridges 6 and 18 of carrier 15 and the electrodes 4 consist of carbon, e.g. graphite. They are then affixed to each other via projections and depressions, as well as within their holders.

The tubular bodies which result from a sensible utilization of the device according to the invention, function primarily as a processing vessel for the production of semiconductor structural components. To this end, the tubes are equipped with semiconductor wafers which are then arranged in a second vessel, sealed to the outside. In this second processing vessel, the atmosphere required for the desired treatment is created. Also, the processing tube consisting of semiconductor material is heated, for example, inductively or by current passage.

If it is desired to precipitate semiconductor wafers upon monocrystalline semiconductor wafers by epi taxy, the tube may serve as a source in a transport reaction. It delivers semiconductor material to a transporting gas known for this purpose so that a gaseous com- -pound results. This compound dissociates under the precipitation of the semiconductor at the surface of the somewhat cooler semiconductor wafers.

The use of the tubes as a processing vessel for doping purposes is also of great importance. Due to an appropriately high doping of the tube which contains the semiconductor wafers to be doped, said dopant, preferably, evaporates during the respective heating and produces, in the interior of the tube, that is at the location of the semiconductor wafers to be doped, the desired doping atmosphere.

We claim:

l. A device for producing tubular bodies of semiconductor material comprising a reaction chamber, within said reaction chamber are at least two vertical tubular carbon carriers each held at their lower ends by an electrode and connected at their upper ends by a conductive bridge, the interior of said tubular carriers serving as a flow through channel for a flowing coolant, and means for introducing reaction gas capable of precipitating the semiconductor into said reaction chamber, and means for heating the carrier, whereby the outer surface of at least one carrier is coated with a layer of the semiconductor by reaction of said reaction gas at said carrier, this semiconductor layer, following the re moval of the carrier, defines the desired semiconductor tube.

2. The device of claim 1, wherein silicon or germa nium is produced and the conductive bridge is carbon.

3. The device of claim 1, wherein said coolant is hydrogen, nitrogen, or argon.

4. The device of claim 3, whereby the bridge that connects the upper ends of the carriers with each other comprises, and the direct holders of the carriers are of the same material as said carriers, the carrier being inserted with its ends into appropriate fitted recesses of said bridge.

5. The device of claim 4, wherein the upper ends of two adjacent carriers are fitted into recesses of the connecting bridge, whereby gaseous coolant, which is introduced at the lower end of the tubular carrier, emerges at the upper end of said carriers, into the reaction chamber.

6. The device of claim 4, wherein both tubular carriers are arranged concentrically to each other.

7. The device of claim 6, wherein the interspace between both concentric carriers and the tubular interior of the inside carrier is provided for flow of the coolant.

8. The device of claim 7, wherein the upper ends of both concentric carriers are interconnected by a bridge, which seals the space between both carriers and the tubular interior of the inside carrier, against the reaction chamber in the wall of the inner carrier, forming a continuous channel service for the passage of the coolant.

9. The device of claim 5, wherein the coolant employed mixes with the gases in the reaction chamber, and is removed with the same.

10. The device of claim 6, wherein tubular concentric carriers are held by electrodes formed by concentric tubes and are heatable by current flowing via said electrodes and the interconnecting bridge.

I? i I t 1 

2. The device of claim 1, wherein silicon or germanium is produced and the conductive bridge is carbon.
 3. The device of claim 1, wherein said coolant is hydrogen, nitrogen, or argon.
 4. The device of claim 3, whereby the bridge that connects the upper ends of the carriers with each other comprises, and the direct holders of the carriers are of the same material as said carriers, the carrier being inserted with its ends into appropriate fitted recesses of said bridge.
 5. The device of claim 4, wherein the upper ends of two adjacent carriers are fitted into recesses of the connecting bridge, whereby gaseous coolant, which is introduced at the lower end of the tubular carrier, emerges at the upper end of said carriers, into the reaction chamber.
 6. The device of claim 4, wherein both tubular carriers are arranged concentrically to each other.
 7. The device of claim 6, wherein the interspace between both concentric carriers and the tubular interior of the inside carrier is provided for flow of the coolant.
 8. The device of claim 7, wherein the upper ends of both concentric carriers are interconnected by a bridge, which seals the space between both carriers and the tubular interior of the inside carrier, against the reaction chamber in the wall of the inner carrier, forming a continuous channel service for the passage of the coolant.
 9. The device of claim 5, wherein the coolant employed mixes with the gases in the reaction chamber, and is removed with the same.
 10. The device of claim 6, wherein tubular concentric carriers are held by electrodes formed by concentric tubes and are heatable by current flowing via said electrodes and the interconnecting bridge. 